The present invention relates generally to 2-dimensional optical fiber arrays. More particularly, it relates to a 2-D fiber array structure and a method for making the structure. 2-D fiber arrays are often used in optical communications and optical switching devices.
Arrays of optical fibers are used in fiber connectors, optical fiber switches (e.g. free space optical switches) and various kinds of sensors and displays. Typically in such optical fiber arrays, the optical fiber must be positioned with high accuracy (e.g. within +xe2x88x921 micron).
1-dimensional (1-D) fiber arrays are commonly manufactured using wet anisotropic etching of  less than 100 greater than  silicon to form V-grooves. Optical fibers placed in the V-grooves are accurately located.
2-dimensional fiber arrays for use in free-space optical switches are currently in high demand. A problem with 2-D optical fiber arrays is that they are very difficult to manufacture with high accuracy.
One technique used to make accurate 2-D fiber arrays is to directionally etch lithographically-defined holes through a wafer of material (e.g. silicon). Optical fibers are then inserted into the holes. The optical fibers are accurately located because the holes are defined lithographically. The holes can be made using reactive ion etching (RIE) or anisotropic wet etching of silicon, for example. A substantial problem with this technique is that inserting optical fibers through holes is very slow and tedious. Often, the optical fibers break during insertion.
Another technique for making 2-D arrays is to stack V-groove chips (e.g. silicon V-groove chips) having V-grooves on both sides of the chip. A substantial problem with this technique is that the location of the optical fibers is dependent upon the thickness of the substrates used to make the V-groove chips. Since it is difficult to control the thickness of substrates to the required tolerances, run-out error occurs in 2-D fiber arrays having several stacked V-groove chips. U.S. Pat. No. 5,044,711 to Saito discloses a 2-D optical fiber array made from stacked V-groove chips.
U.S. Pat No. 5,483,611 to Basavanhally discloses a 2-D optical fiber array having stacked 1-D V-groove arrays. The apparatus of Basavanhally employs mechanical adjustments for positioning the 1-D V-groove fiber arrays.
U.S. Pat No. 4,407,562 to Young discloses an optical switch having a 2-D fiber array made from wafers having V-grooves. The 2-D fiber array is made from stacked V-groove chips.
U.S. Pat. No. 3,864,018 to Miller discloses a 2-D fiber array made from a stack of V-groove chips. The thickness of the V-groove chips must be accurately controlled for accurate fiber positioning.
U.S. Pat. No. 4,046,454 to Pugh et al. discloses yet another 2-D fiber array made from stacking V-groove chips. The fiber array of Pugh et al. has layers of compliant material that press optical fibers into the V-grooves.
U.S. Pat. No. 5,146,532 to Hodge discloses an optical fiber retaining device for holding optical fibers. The device has interlocking plastic pieces that can be stacked. The fiber holder of Hodge is not suitable for making precision 2-D optical fiber arrays.
There exists a need in the art of optical fiber devices for an accurate 2-dimensional fiber array that is easy to assemble. Such a 2-D fiber array would be useful for making optical switches and other devices.
Accordingly, it is a primary object of the present invention to provide a 2-dimensional optical fiber array that:
1) is easy to assemble and does not require insertion of optical fibers through tiny holes;
2) provides extremely accurate alignment of optical fibers;
3) provides for arbitrary 2-D fiber arrangements (e.g. hexagonal grid, square grid) defined according to a lithographic pattern;
4) does not require the use of chips having accurately defined thickness.
These and other objects and advantages will be apparent upon reading the following description and accompanying drawings.
These objects and advantages are attained by a 2-D optical fiber array having a plurality of stacked, etched sticks, and an optical fiber disposed between the etched sticks. The etched sticks have notches that form cages for holding the optical fibers. The notches have surfaces that are directionally dry-etched in a direction perpendicular to a front surface the array (the optical fiber is roughly perpendicular to the front surface).
The etched sticks may have top and bottom surfaces that are directionally dry etched. Alternatively, the etched sticks have top and bottom surfaces that are cleaved surfaces. In case the top and bottom surfaces are cleaved, the etched sticks are stacked so that complementary cleaved surfaces are adjacent to one another.
The etched sticks can also have alignment holes and alignment rods disposed in the alignment holes of the etched sticks. The alignment holes and alignment rods are oriented perpendicular to the optical fibers and extend through an interior of the etched sticks. Also, the front surface of the 2-D array can have etched pits or grooves (e.g. anisotropically etched V-grooves).
The etched sticks can be diffusion bonded together, glued together (e.g. with epoxy), or adhered together with materials such as spin-on-glass (SOG) or sol-gel materials. Preferably, the etched sticks are made of silicon.
In an alternative embodiment of the invention, the notches are not necessarily dry etched, but are made according to many other techniques such as laser drilling. In this embodiment, the top and bottom surfaces of the etched sticks are necessarily cleaved or directionally dry etched.
The present invention also includes a method for making the etched sticks by making a perforated chip having a 2-D array of holes. The perforated chip is cleaved to separate it into etched sticks. The cleave lines necessarily intersect the holes so that fibers can be placed in the resulting notches.